Here are the results of the benchmarks. The number represents requests / second.
Higher is better.

frameworks

req/s

ruby on rails

48.73

restify

8117.63

spark

32634.10

I knew Ruby on Rails is slow, but I had no idea that it’s this slow. And on
the other hand, I knew Java web frameworks are generally fast, but I had no
idea that Spark is that fast! And Restify occupies a sweet spot between
Ruby on Rails and Spark.

We can draw some conclusions from the findings.

Use Spark for very highly trafficked microservices that requires requests
to be served at low latency

Use Restify for all kinds of backend API when you want to leverage a vast
catalog of Node.js packages and great development tools

Reserve using Ruby on Rails for product oriented application only.
I would not recommend Ruby on Rails for backend API that needs to
serve a large traffic.